The present invention relates to a multi-circuit air-brake system, in particular for motor vehicles, with compressed-air supply means, safety valves in a number equal to the number of circuits, supply tanks in a number equal to the number of circuits, and a multi-circuit brake valve connected between the supply tanks and the brake lines. Air brake systems of this type have been previously known from German Pat. No. 1,176,500 and German Pat. No. 1,175,095. Each safety valve is incorporated in a line coming from a pressure regulator of the compressed-air supply means, with individual lines in a number corresponding to the number of circuits leading from the safety valves to different supply tanks. The safety means of each safety valve comprises essentially a spring-loaded piston-like control element so that to make the safety means of the safety valve open each pressure supplied by the compressed-air supply means must first overcome the spring pressure.
Considering that safety valves of the prior art, which may also have a multi-circuit design, are incorporated in a line between the pressure regulator and the supply tanks, it is obvious to one skilled in the art that a simplified construction, may be obtained by designing these safety valves to form a part of either the pressure regulator or the supply tanks. German laid-open Patent Application No. 2,233,144 suggests, for instance, a pressure regulator including a safety valve. However, this arrangement offers the disadvantage that separate lines must be provided to connect each individual supply tank with the pressure regulator and the safety valve incorporated therein.
The above described safety valves are intended to protect brake circuits associated with the tractor and/or the trailer of a motor truck-trailer type of vehicle. German laid-open Patent Application No. 2,127,833 discloses an arrangement in which a safety valve is incorporated in the trailer control valve in order to protect the trailer brake circuit.